The present invention relates to a vehicle seat and more specifically to a vehicle seat comprising a back and forth slide mechanism comprising a fixed rail and a movable rail for supporting a seat cushion and a reclining apparatus comprising a base member fixed to said seat cushion, a rotational arm swingably supported by said base member and fixed to a seat back, a lock mechanism encased between said base member and said rotational arm, an operating lever unlocking said lock mechanism, a lock spring urging said operating lever to a locking direction and a return spring inclining the seat back forward.
Hitherto, a construction adjusting back and forth movement of a seat cushion by a back and forth slide mechanism is well known. Two reclining apparatuses inclining a seat back forward and rearward are described in Japanese Unexamined (KOKAI) Patent Publication No. 9 (1997)-28496 and Japanese Unexamined (KOKAI) Patent Publication No. 9 (1997)-131237 suggested by the present applicant. Japanese Examined (KOKOKU) Patent Publication No. 63 (1988)-65327 discloses a hinge apparatus for a reclining backrest capable of locking according to an adjusting position. Japanese Unexamined (KOKAI) Patent Publication No. 7 (1995)-136032 discloses a construction in which a cam is moved along only a sliding direction (up and down direction) of a pole in order to avoid an inferior connection by a dimension error of the pole and the cam.
The Japanese Unexamined (KOKAI) Patent Publication No. 9 (1997)-28496 discloses two reclining apparatuses in which a bulging portion is provided with a first cam portion for unlocking the cam portion of an inner side and a second cam portion for locking respectively, at a time of lock-off and lock-on, the bulging portion is engaged with a groove for lock-off of teeth inner and an abutment for lock-on, engagement and disengagement with outer teeth of teeth inner and inner teeth of an arm fixed to a seat back side and lock-off and lock-on are performed prior to the outer side.
A return spring is mounted in order to incline a seat back forward, the return spring is mounted on a free hinge side of one side lock because installation positions are few when each of a base member and a rotational arm is circular.
As shown in FIGS. 5 and 6, a reclining apparatus 10 comprising a base member 11 fixed to a movable rail side, a rotational arm 12 swingably supported by the base member 11 and fixed to a seat back side, a lock mechanism (not shown in the drawing) encased between said base member 11 and said rotational arm 12, an operating lever 15 unlocking said lock mechanism, a lock spring 35 urging the operating lever 15 to a locking direction and a return spring 45 inclining the seat back forward is well known.
One end 45a of said return spring 45 is engaged with a hook portion 34 formed in the rotational arm 12, the other end 45b of the return spring 45 is engaged with a hook bracket 47 formed in said base member 11, the hook bracket 47 is curvedly extended and is formed in a guide portion 51 for said return spring 45. The guide portion 51 produces a resilient force efficiently so that a smooth operation is gained.
In this conventional example, however, when each of the base member and the rotational arm is circular, installation positions of the return spring are few and it is difficult for two reclining apparatuses to fix the return spring. Especially when each of the base member and the rotational arm is circular, when the rotational arm is fixed to a lower portion of the side frame of the seat back frame by stud bolts, the return spring is forced to be positioned outside in order to avoid engagement with the stud bolts and thereby the reclining apparatuses become thick and it is necessary to mount parts when the angle limiting portion of the front and rear inclination of the seat back is formed, it is necessary to mount the guide portion to a hook bracket in order to gain a smooth operation of the return spring and thereby the number of parts increases and the manufacturing cost becomes high.